1. Field of the Invention
The present invention relates to an antimicrobial treatment method for heat exchangers and evaporators, especially those used in automotive air conditioners and the like.
2. Related Art
The heat exchanger disclosed in the Japanese Patent Unexamined Publication 1983/102,073, employs a method of preventing odors in the air blown out from the air conditioner that comprises the application of an organic polymer film containing a fungicide, an antiseptic, a deodorant and a surface active agent on the heat exchanger. As a means of hydrophilic treatment, anti-corrosion treatment, mildew proofing and sterilization treatment, the heat exchanger is immersed in a solution in which a surface active agent, a mildew proofing agent, an antiseptic and a deodorant are dissolved, to apply the aforementioned organic polymer film on the heat exchanger, which is then air dried.
Also, in the heat exchanger that is disclosed in the Japanese Patent Unexamined Publication 1985/50,397, an organic polymer resin film containing a disinfectant of low solubility in water is formed on the corrugated fins and then a hydrophilic treatment is applied on top of it to prevent water from collecting on the corrugated fins and the attendant problems this gives rise to, including, for example, increased ventilation resistance, water splashing on the corrugated fins, corrosion of the corrugated fins, propagation of microorganisms and mildew and malodor caused by dust contamination. In this method, the heat exchanger is immersed in a mixed solution which comprises a disinfectant dissolved into a hydrophilic-treatment liquid to form the aforementioned organic polymer film, which is then dried in a hot air circulating dryer.
Furthermore, in the heat exchanger disclosed in Japanese Patent Unexamined Publication 1987/129,695, a film, comprising an anticorrosion film and a hydrophilic film, at least one of which contains an antiseptic, is formed. Also, in the heat exchanger disclosed in the Japanese Patent Unexamined Publication 1990/101,395, a hydrophilic film that includes a first fast-acting antimicrobial agent and a second slow-acting antimicrobial agent is provided. Furthermore, in the heat exchanger disclosed in the Japanese Patent Unexamined Publication 1989/10,072, a disinfectant that is coated with a film such as a synthetic resin with varying degrees of solubility is dispersed in the surface film. In the heat exchanger that is disclosed in the Japanese Patent Unexamined Publication 1989/314,158, a silicon-type film with an antimicrobial agent dispersed in it is provided on the corrugated fins. Furthermore, in the heat exchanger that is disclosed in the Japanese Patent Unexamined Publication 1991/177,796, a resin film containing a mildew-proofing agent is formed on top of a hydrophilic film. In the heat exchanger that is disclosed in the Japanese Patent Unexamined Publication 1991/244,997, a hydrophilic film mixed with a germicide and a mildew proofing agent is provided.
Also, in Japanese Patent Unexamined Publication 1991/51,698, a heat exchanger is disclosed wherein part of the film that is formed on the surface of the fins that contains an antimicrobial agent is a resin that possesses the property of becoming porous after being dissolved in water.
Furthermore, in the Japanese Patent Unexamined Publication 1991/195,894, a mildew-proofing compound is disclosed wherein a solution in which the mildew-proofing substance has been dissolved is mixed at a specific ratio with a resin film-forming solution to achieve a specific ratio (0.2-50, weight %) of the mildew-proofing substance to the resin film.
In manufacturing the aforementioned heat exchangers, if an antimicrobial agent is mixed in a liquid resin or in a hydrophilic-treatment liquid, a specific amount of antimicrobial agent is present in the hydrophilic film on the surface. This method has the advantage that the antimicrobial agent will have a long lasting effect. However, because there is a limit to the solubility of the antimicrobial agent, there is also a limit to the degree of antimicrobial action.
There is another method in which an antimicrobial agent is applied by means of spraying after the hydrophilic treatment and the drying treatment are completed. This method has the advantage of providing excellent immediate effect. On the other hand, because the antimicrobial agent is applied only superficially with this method, it presents the problem that the antimicrobial agent will be washed away by condensation water, resulting in a short-term antimicrobial effect.